Wireless Local Area Networks (WLANs) are being contemplated or are known. Voice services in WLANs are typically supported by WLAN servers that may be referred to as private branch exchanges (PBXS) or enterprise servers. The PBX normally provides a control and switching function for the WLAN and communication units operating therein or users thereof. The WLAN can be an attractive and inexpensive alternative for typical voice services such as telephony or dispatch services and may provide additional amenities such as high-speed wireless Internet and Intranet access as well as other real-time applications that may be more specific to a given enterprise.
Wireless wide area networks (wireless WANs or WANs), such as conventional cellular telephone systems, are also known. Such networks provide the advantage of wide area coverage but may not be economically attractive for routine access to wideband or high speed data capabilities, such as are required for certain Internet or Intranet applications. Nevertheless a communication unit that is operating on a WLAN may move beyond the effective service area for the WLAN and thus need support or services from a WAN. In situations, sometimes referred to as loosely coupled systems, where the WAN is indirectly coupled to the WLAN via the public switched telephone network (PSTN) or communication unit operating thereon this can present problems, particularly for on-hold calls within the WLAN after a handoff or handover (hand out) of a communication unit to the WAN. Current practice in such loosely coupled systems is to disconnect the on-hold calls or route them to voice mail. In either event the call is no longer available to the communication unit or user thereof, thus contributing to inconvenience and lack of satisfaction.
Therefore, a need exists for methods and apparatus to facilitate on hold call retrieval and routing for communication units operating within such loosely coupled communications networks